The Austrian branch of the hacker group Anonymous accessed the bank data of 96,000 people in an attack on the website of the country's GIS television licence agency, officials said on Monday.
The hacker group, which was targeted last week by US authorities in a crackdown that included 16 arrests, managed to access 214,000 records with personal data during an attack on Friday.
Banking data of 96,000 people was among these records on the GIS server.
"We have already started to inform all the clients concerned personally and advise them to monitor especially closely all their bank account movements," GIS spokesman Herbert Denk said.
The federal security and counter-terrorism bureau (BVT) was investigating the attack and planned to file a complaint against unknown persons, GIS added.
The Anonymous hackers had also recently attacked the websites of Austria's far-right Freedom Party and the Social-Democrats of Chancellor Werner Faymann.